U.S. patent number 5,777,340 [Application Number 08/877,726] was granted by the patent office on 1998-07-07 for ophthalmic photographic device.
This patent grant is currently assigned to Nikon Corporation. Invention is credited to Yasunori Ueno.
United States Patent |
5,777,340 |
Ueno |
July 7, 1998 |
Ophthalmic photographic device
Abstract
An ophthalmic photographic device includes an illumination
optical system for irradiating a fundus oculi of an eye to be
examined with illuminating light, a photographic optical system to
photograph fundus oculi, an indicator projecting optical system for
projecting an indicator on the fundus oculi, and a focusing
detection optical system which has a photoelectric converter
receiving light of the indicator projected on the fundus oculi and
detects focus information based on an output from the photoelectric
converter. According to the present invention, the ophthalmic
photographic device further includes a barrier filter for
fluorescent photography which is used in fluorescent photography to
cut off exciting light and to transmit fluorescent light from the
fundus oculi and light having longer wavelengths than the
fluorescent light over a predetermined wavelength range, and a
barrier filter for infrared fluorescent photography which is used
in infrared fluorescent photography to cut off exciting light and
to transmit infrared fluorescent light from the fundus oculi and
light having longer wavelengths than the infrared fluorescent light
over a predetermined wavelength range. The barrier filters are
adapted to be selectively used according to photographic
conditions.
Inventors: |
Ueno; Yasunori (Kanagawa-ken,
JP) |
Assignee: |
Nikon Corporation (Tokyo,
JP)
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Family
ID: |
15051743 |
Appl.
No.: |
08/877,726 |
Filed: |
June 18, 1997 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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445101 |
May 19, 1995 |
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Foreign Application Priority Data
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May 20, 1994 [JP] |
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6-131174 |
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Current U.S.
Class: |
250/458.1;
351/206 |
Current CPC
Class: |
A61B
3/145 (20130101) |
Current International
Class: |
A61B
3/14 (20060101); A61B 003/14 (); G03B 003/00 () |
Field of
Search: |
;250/458.1,459.1
;351/206 |
References Cited
[Referenced By]
U.S. Patent Documents
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4412728 |
November 1983 |
Sakane et al. |
4436388 |
March 1984 |
Takahashi et al. |
5181055 |
January 1993 |
Sano et al. |
5291231 |
March 1994 |
Hideshima et al. |
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Foreign Patent Documents
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61-122837 |
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Jun 1986 |
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JP |
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62-41637 |
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Feb 1987 |
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JP |
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Primary Examiner: Glick; Edward J.
Attorney, Agent or Firm: Armstrong, Westerman, Hattori,
McLeland & Naughton
Parent Case Text
This application is a continuation of application Ser. No.
08/445,101 filed May 19, 1995, now abandoned.
Claims
What is claimed is:
1. An ophthalmic photographic device comprising:
an illumination optical system for irradiating a fundus oculi to be
examined with illuminating light said illumination system
comprising a wavelength separating member;
a photographic optical system for photographing the fundus
oculi;
an indicator projecting optical system for projecting an indicator
on the fundus oculi via said wavelength separating member of said
illumination optical system;
a focusing detection optical system which has a photoelectric
converter receiving light of the indicator projected on the fundus
oculi and detects focusing information based on an output from said
photoelectric converter, said focusing detection optical system
including a dichroic mirror which reflects light having
substantially longer wavelengths than a center wavelength of
infrared fluorescent light for use in detecting focusing
information;
a barrier filter for fluorescent photography which cuts off
exciting light in fluorescent photography and transmits, over a
predetermined wavelength range, fluorescent light and light having
a longer wavelength than fluorescent light, both of which are
emitted from the fundus oculi;
a barrier filter for infrared fluorescent photography which cuts
off exciting light in infrared fluorescent photography and
transmits, over a predetermined wavelength range, infrared
fluorescent light and light having a longer wavelength than
infrared fluorescent light, both of which are emitted from the
fundus oculi; and
said barrier filters being adapted to be selectively used according
to photographic conditions;
wherein a luminescence center wavelength of a light source of said
indicator projecting optical system is substantially longer than a
center wavelength of infrared fluorescent light in infrared
fluorescent photography, so that said barrier filters for
fluorescent photography and for infrared fluorescent photography
transmit light emitted from the light source of said indicator
projecting optical system.
2. An ophthalmic photographic device according to claim 1, wherein
said barrier filters for fluorescent photography and for infrared
fluorescent photography are adapted to be selectively placed in a
common optical path of said photographic optical system and said
focusing detecting optical system.
3. An ophthalmic photographic device according to claim 2, wherein
said barrier filters for fluorescent photography and for infrared
fluorescent photography are adapted to be selectively placed in the
common optical path between an aperture stop and a wavelength
separating member.
4. An ophthalmic photographic device according to claim 2, further
comprising an exciter filter transmits light having an absorption
center wavelength in fluorescent photography and an exciter filter
transmits light having an absorption center wavelength in infrared
fluorescent photography, which exciter filters are adapted to be
selectively placed in an optical path of said illumination optical
system.
5. An ophthalmic photographic device according to claim 4, wherein
said exciter filters are adapted to be selectively placed in the
optical path between a stroboscopic tube and said wavelength
separating member in said illumination optical system.
6. An ophthalmic photographic device according to claim 1, further
comprising an exciter filter transmits light having an absorption
center wavelength in fluorescent photography and an exciter filter
transmits light having an absorption center wavelength in infrared
fluorescent photography, which exciter filters are adapted to be
selectively placed in an optical path of said illumination optical
system.
7. An ophthalmic photographic device according to claim 6, wherein
said exciter filters are adapted to be selectively placed in the
optical path between a stroboscopic tube and said wavelength
separating member in said illumination optical system.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an ophthalmic photographic device,
and more specifically to a retinal camera capable of detecting
focusing in fluorescent fundus oculi photography and in infrared
fluorescent fundus oculi photography as well as in ordinary
photography.
2. Description of the Prior Arts
Conventional ophthalmic photographic devices like a retinal camera
are known which can practice not only ordinary photography but also
so-called fluorescent photography. In ordinary photography, an
image of a fundus oculi to be examined is taken on color film,
while in fluorescent photography, light having wavelengths in a
specific visible wavelength range is projected on the fundus oculi
to be examined and an image of blood vessels of the fundus oculi is
taken by means of fluorescent light emitted from the blood vessels
of the fundus oculi, which fluorescent light is exhibited by a
fluorescent substance injected into an examinee.
As described above, in conventional ophthalmic photographic devices
like a retinal camera, visible light is projected on the fundus
oculi to be examined in ordinary and fluorescent photography. This
has given rise to a problem that the state of a choroid located
behind a retina cannot be observed or photographed with respect to
a macula portion containing tissue which is opaque to visible
light.
Thus, in order to detect in a patient senile macular degeneration
or the like in its early stages, it has been practiced that
infrared light having wavelengths in a specific wavelength range is
projected on the fundus oculi to be examined to thereby observe and
photograph the state of the choroid located behind the retina by
means of infrared fluorescent light from the choroid coat.
Generally, it is difficult to focus on the fundus oculi for devices
for observing or measuring an eye due to an insufficient quantity
of light or poor contrast derived from a low reflectance of the
fundus oculi. Particularly, observing an image of a fundus oculi by
means of fluorescent light or infrared fluorescent light has
involved a problem that it is more difficult for equipment
(photographic optical system and observational optical system) to
focus on a fundus oculi because an image of the fundus oculi to be
observed has no coloration (if an observation system is a TV
monitor, a monochromatic image will be displayed thereon) with
resulting poor contrast.
SUMMARY OF THE INVENTION
A main object of the present invention is to provide an ophthalmic
photographic device capable of detecting focusing in fluorescent
photography and in infrared fluorescent photography as well as in
ordinary photography.
Another object of the present invention is to provide an ophthalmic
photographic device capable of detecting focusing in any of
ordinary photography, fluorescent photography, and infrared
fluorescent photography by selectively using a barrier filter for
fluorescent photography and a barrier filter for infrared
fluorescent photography.
A further object of the present invention is to provide an
ophthalmic photographic device capable of detecting focusing in any
of ordinary photography, fluorescent photography, and infrared
fluorescent photography by selectively using an exciter filter for
fluorescent photography and an exciter filter for infrared
fluorescent photography in combination with the barrier filter for
fluorescent photography and the barrier filter for infrared
fluorescent photography.
The ophthalmic photographic device according to the present
invention has an illumination optical system for irradiating a
fundus oculi to be examined with illuminating light; a photographic
optical system for photographing the fundus oculi; an indicator
projecting optical system for projecting an indicator on the fundus
oculi; a focusing detection optical system which has a
photoelectric converter receiving light of the indicator projected
on the fundus oculi and detects focusing information based on an
output from said photoelectric converter; a barrier filter for
fluorescent photography which cuts off exciting light in
fluorescent photography and transmits, over a predetermined
wavelength range, fluorescent light and light having a longer
wavelength than fluorescent light, both of which are emitted from
the fundus oculi; a barrier filter for infrared fluorescent
photography which cuts off exciting light in infrared fluorescent
photography and transmits, over a predetermined wavelength range,
infrared fluorescent light and light having a longer wavelength
than infrared fluorescent light, both of which are emitted from the
fundus oculi. The barrier filters are adapted to be selectively
used according to photographic conditions.
The barrier filter for fluorescent photography and the barrier
filter for infrared fluorescent photography have a disadvantage in
that extending their transmission characteristics to a shorter
wavelength side allows even exciting light, together with
fluorescent light and infrared fluorescent light, to pass
therethrough. However, extending the transmission characteristic to
the longer wavelength side does not bring about such a
disadvantage. The present invention pays attention to this fact.
The wavelength characteristic of the barrier filters is extended to
the longer wavelength side so as not to transmit exciting light
used in fluorescent photography and exciting light used in infrared
fluorescent photography and to have no effect on photography. Thus,
the ophthalmic photographic device is adapted for use in any of
ordinary photography, fluorescent photography, and infrared
fluorescent photography. That is, in ordinary photography, the
barrier filters are not used at all, and in fluorescent
photography, the barrier filter for fluorescent photography is used
to prevent exciting light for fluorescent photography from
advancing through the photographic optical system and to transmit
light having useful wavelengths for fluorescent photography,
thereby facilitating the focusing detection. Also, in infrared
fluorescent photography, the barrier filter for infrared
fluorescent photography is used to prevent exciting light from
advancing through the photographic optical system and to transmit
light having useful wavelengths for infrared fluorescent
photography, thereby facilitating the focusing detection.
In an embodiment of the present invention, a luminescence center
wavelength of the light source of the indicator projecting optical
system is substantially longer than a center wavelength of infrared
fluorescent light in infrared fluorescent photography, so that the
barrier filters for fluorescent photography and for infrared
fluorescent photography can transmit light emitted from the light
source of the indicator projecting optical system. Also, the
barrier filters for fluorescent photography and for infrared
fluorescent photography may be selectively placed in a common
optical path of the photographic optical system and the focus
detecting optical system.
In another embodiment, an exciter filter which transmits light
having an absorption center wavelength in fluorescent photography
and an exciter filter which transmits light having an absorption
center wavelength in infrared fluorescent photography may be
provided, and the exciter filters may be selectively placed in the
optical path of the illuminating optical system. Also, the exciter
filters may be selectively disposed in the optical path between a
stroboscopic tube and a wavelength separating member (a dichroic
prism, in the embodiment of this application) in the illuminating
optical system.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic diagram wing the construction of an
ophthalmic photographic device according to an embodiment of the
present invention.
FIG. 2 is a partial diagrammatic view showing a focus detecting
optical system of the ophthalmic photographic device of FIG. 1.
FIG. 3 is a view showing an opening of a ring slit.
FIG. 4 is a view showing a slit formed in an indicator plate of
FIG. 1.
FIG. 5 is an external view of a pupil splitting prism of FIG.
1.
FIG. 6 is a diagram illustrating the principle of focusing
detection.
FIG. 7(a) is a graph showing a characteristic of an exciter filter
used in fluorescent photography.
FIG. 7(b) is a graph showing a characteristic of an exciter filter
used in infrared fluorescent photography.
FIG. 8(a) is a graph showing a characteristic of a barrier filter
used in fluorescent photography.
FIG. 8(b) is a graph showing a characteristic of a barrier filter
used in infrared fluorescent photography.
DESCRIPTION OF THE PREFERRED EMBODIMENT
An embodiment of the present invention will now be described with
reference to the drawings.
FIG. 1 is a schematic diagram showing the construction of an
ophthalmic photographic device according to an embodiment of the
present invention. An ophthalmic photographic device 100 comprises
an illumination optical system 101 for illuminating a fundus oculi
to be examined or tested, an indicator or collimating mark
projecting optical system 102 for projecting an indicator or
collimating mark on the fundus oculi, a focusing detection optical
system 103 for receiving light of the indicator projected on the
fundus oculi thereby to detect focusing on the fundus oculi, an
observational optical system 104 for observing the state of the
fundus oculi, and a photographic optical system 105 for
photographing the state of the fundus oculi.
In FIG. 1, the illuminating optical system 101 includes a ring slit
5, a relay lens 6, a relay lens 2 for a light source 1, and a
reflecting mirror 3. Light emitted from a light source 1 for
observational illumination impinges on the reflecting mirror 3
through the relay lens 2 for a light source, and then is reflected
upward in the figure. Light reflected by the reflecting mirror 3
impinges on the relay lens 6 through the ring slit 5.
A stroboscopic tube 4 is disposed as a light source for
photographic illumination in a position where it is conjugated with
the light source 1 for observational illumination by the relay lens
2 for a light source. Furthermore, as shown in FIG. 3, the ring
slit 5 has an opening of a circular slit with an optical axis as a
center thereof. An exciter filter 30a for fluorescent photography
and an exciter filter 30b for infrared fluorescent photography are
adapted to be selectively inserted between the ring slit 5 and the
relay lens 6 for a ring slit.
The illumination optical system 101 further includes a wavelength
separating member (a dichroic prism, in this embodiment) 7, a relay
lens 8, an apertured mirror 9, and an objective lens 11, which
components are all shared by the collimating mark or indicator
projecting optical system 102. Light having passed through the
relay lens 6 for a ring slit (light from the light source 1 for
observational illumination and light from the stroboscopic tube 4)
passes through the dichroic prism 7 and then impinges on the
apertured mirror 9 through another relay lens 8 for a ring slit.
Light reflected leftward in the figure by the apertured mirror 9
illuminates the fundus oculi of an eye 12 to be examined through
the objective lens 11. As is well known, an operating distance
between the device of the present embodiment and the eye 12 to be
examined is adjusted so that the ring slit 5 is positioned so as to
be substantially conjugated with the cornea of the eye 12 to be
examined by the two relay lenses 6 and 8 for a ring slit and the
objective lens 11.
On the other hand, the indicator projecting optical system 102 has
a light source (point light source) 16 projecting an indicator or
collimating mark and consisting of an infrared light emitting diode
for example, a pair of relay lenses 17a and 17b, and an indicator
plate 18 placed between the relay lenses 17a and 17b. Infrared
light (indicated by a two dots-and-dash line in the figure) emitted
from the light source 16 for projecting an indicator illuminates
the indicator plate 18 through the relay lens 17a for the indicator
projecting system. As shown in FIG. 4, a slit extending in parallel
with the paper surface is formed in the indicator plate 18.
Beams of light having passed through the slit are once focused and
then impinge on the dichroic prism 7 through the relay lens 17b for
the indicator projecting system. Beams of light incident on the
dichroic prism 7 are reflected upward by the reflecting surface
thereof and then are refocused near the aperture mirror 9 through
the relay lens 8 for a ring slit. Beams of light reflected leftward
in the figure by the apertured mirror 9 are focused near the pupil
of the eye 12 to be examined through the objective lens 11, thereby
illuminating the fundus oculi.
In the above-mentioned illumination optical system 101 and
indicator projecting optical system 102, the dichroic prism 7 has
the characteristic of reflecting infrared light and of transmitting
visible light. Accordingly, visible light from the light source 1
for observational illumination and from the stroboscopic tube 4
(light source for photographic illumination) passes through the
dichroic prism 7 and advances toward the relay lens 8, while
infrared light from the light source 1 for observational
illumination and the stroboscopic tube 4 is reflected by the
dichroic prism 7 to get out of the illuminating optical system. On
the other hand, infrared light from the light source 16 for
projecting an indicator is reflected by the dichroic prism 7 and
then advances toward the relay lens 8.
As indicated by a dotted line in FIG. 1, rays of light having
passed through the slit in the indicator plate 18 are focused near
the dichroic prism 7 by the relay lens 17b for the indicator
projecting system and then are reflected upward in the figure. The
reflected beams of light are focused at a rear focal point of the
objective lens 11 through the relay lens 8 and the apertured mirror
9. Thus, light having passed through the slit becomes substantially
parallel beams of light after passing through the objective lens
11, and then enters the eye 12 to be examined. As a result, if the
eye 12 to be examined is an emmetropia, an image of the slit in the
indicator plate 18 is formed on the fundus oculi. In other words,
an image of the slit in the indicator plate 18 (indicator image)
defocuses according to the diopter of the eye 12 to be
examined.
FIG. 2 is a partial diagrammatic view showing the structure of the
focusing detecting optical system 103 of the ophthalmic
photographic device of FIG. 1. The focusing detection optical
system 103 includes a relay lens 13 for focusing, a wavelength
separating member (a dichroic mirror, in this embodiment) 14, a
field stop 19, a field lens 20 placed adjacent to the field stop
19, a refocusing lens 21, a pupil splitting prism 22 placed
adjacent to the refocusing lens 21, and an array sensor 23. The
observational optical system 104 and the photographic optical
system 105, described later, share the relay lens 13 for focusing
and the dichroic mirror 14. The field stop 19 is positioned so as
to be conjugated with the array sensor 23 by the refocusing lens
21.
As indicated with a solid line in FIG. 2, an image of the slit in
the indicator plate 18 projected on the fundus oculi of the eye 12
to be examined serves as a secondary light source. Beams of light
from the secondary light source are once focused through the
objective lens 11, pass through a center opening in the apertured
mirror 9 and an aperture stop 10, and then enter the relay lens 13
for focusing. Infrared light having passed through the relay lens
13 for focusing impinges on the dichroic mirror 14 which has the
characteristic of reflecting infrared light and of transmitting
visible light. Beams of light reflected upward in the figure by the
dichroic mirror 14 are once focused near the field stop 19 and then
enter the field lens 20. Light having passed through the field lens
20 impinges on the array sensor 23 through the refocusing lens 21
and the pupil splitting prism 22.
In FIG. 1, the observational optical system 104 includes the relay
lens 13 and dichroic mirror 14, which are shared by the focusing
detection optical system 103, a quick return mirror 27, a mirror
28, and an eyepiece 29. The photographic optical system 105 has the
shared relay lens 13 and dichroic mirror 14, and a photographic
image plane 15. The array sensor 23 is positioned to be conjugated
with the photographic image plane 15 and the image plane (not
shown) of the eyepiece 29. A refocusing or image reforming lens, or
TV image plane (both not shown) may be used in place of the
eyepiece or an examiner or observer. This is preferable, in
particular, the infrared fluorescent photography. Beams of
reflected light from the fundus oculi of the eye 12 to be examined,
which fundus oculi is illuminated by visible light from the light
source 1 for observational illumination and the stroboscopic tube 4
(light source for photographic illumination), pass through the
dichroic mirror 14 and then are focused on the photographic image
plane 15. Since the quick return mirror 27 is located between the
dichroic mirror 14 and the photographic image plane 15, the
reflected visible light from the fundus oculi having passed through
the dichroic mirror 14 is reflected upward in the figure by the
quick return mirror 27 and then is led to the eyepiece 29 via the
mirror 28 for observation by an examiner 40. The quick return
mirror 27, mirror 28, eyepiece 29, and examiner 40 are not shown in
FIG. 2.
Thus, the fundus oculi to be examined can be observed through the
eyepiece 29 and photographed on the photographic image plane
15.
As has been described above, the dichroic prism 7 has the
characteristic of reflecting infrared light and of transmitting
visible light, and hence the fundus oculi of the eye 12 is
illuminated by infrared light from the light source 16 for
projecting an indicator or collimating mark and by visible light
from the light source 1 for observational illumination and the
stroboscopic tube 4.
Also, since the dichroic mirror 14 has the characteristic of
reflecting infrared light and of transmitting visible light, only
light which has passed through the indicator plate 18 illuminated
with the light source 16 for projecting an indicator, reaches the
array sensor 23. As a result, an indicator image (a slit image in
the present embodiment) is formed with good contrast on the array
sensor 23.
The barrier filter 31a for fluorescent photography and the barrier
filter 31b for infrared fluorescent photography are adapted to be
selectively inserted between the relay lens 13 for focusing and the
dichroic mirror 14. This intends to pass only desired fluorescent
light through the barrier filter in view of the fact that when
fluorescent injected into blood vessels absorbs exciting light and
emits fluorescent light, wavelength of fluorescent light shifts to
the longer wavelength side than exciting light.
Thus, beams associated with the slit image (indicator image) from
the fundus oculi of the eye 12 are focused near the array sensor 23
by the refocusing lens 21. At this time, the pupil splitting prism
22 causes a luminous flux to be split in half when the luminous
flux passes therethrough. Each split luminous flux is focused on
the array sensor 23 in mutually different areas (cells), as shown
in FIG. 2.
A perspective view of the pupil splitting prism 22 is shown in FIG.
5. In FIGS. 1 and 2, the ridge line of the pupil splitting prism 22
is perpendicular to the paper surface for convenience of
representation. In actual disposition, however, the pupil splitting
prism 22 is turned 90 degrees from the illustrated position about
the optical axis so that the ridge line thereof is in parallel with
the paper surface. As a result, cells of the array sensor 23 are
arrayed perpendicular to the paper surface to be consistent with
the direction of the ridge line of the pupil splitting prism 22.
Thus, it is desirable for the longitudinal direction of the slit
image and the direction of the ridge line of the pupil splitting
prism 22 to match.
As indicated by a dotted line in FIG. 2, the ridge line of the
pupil splitting prism 22 is substantially conjugated with the
aperture diaphragm 10 by the relay lens 13 for focusing and the
field lens 20. Since the aperture stop 10 is equivalent to an exit
pupil of the focusing detection optical system 103, images on the
array sensor 23 are formed by luminous flux from two different
portions of the pupil of the optical system. Thus obtained two
images on the array sensor 23, as is well known, shift laterally
with respect to each other according to a so-called front focus
state and rear focus state. Accordingly, by measuring the distance
between the two images on the array sensor 23, the focusing state
can be detected.
In details, assuming that the distance between the two images on
the array sensor 23 is L in the focused state, as indicated by a
solid line in FIG. 6, when a focused point is located on the rear
side of the field stop 19 (above the field stop 19 in the figure),
such as in the rear focus state, the distance between images
becomes smaller than the reference distance L, as indicated by a
dotted line in the figure. On the other hand, when a focused point
is located on the front side of the field stop 19 (below the field
stop 19 in the figure), such as in the front focus state, the
distance between images becomes larger than the reference distance
L (not shown).
As has been described above, focusing information can be obtained
by measuring the distance between two slit images on the array
sensor 23 and by comparing the measured distance with a reference
distance.
As shown in FIG. 1, cells of the array sensor 23 are sequentially
driven based on signals from a drive means 24, and
photoelectrically converted signals corresponding to the cells are
sequentially outputted from the array sensor 23 to an arithmetic
means 25. The arithmetic means 25 measures the distance between two
slit images based on photoelectrically converted signals from the
array sensor 23 and compares the measured distance with a reference
distance measured in the focused state. Based on the focusing
information thus obtained by the arithmetic means 25, a motor M is
driven through a motor drive means 26 to move the relay lens 13 for
focusing along the optical axis as needed thereby to focus the
array sensor 23 on the fundus oculi of the eye 12 to be examined.
This, in turn, focuses the photographic image plane 15 and the
image plane (not shown) of the eyepiece 29 on the fundus oculi.
Incidentally, wavelengths required for ordinary fundus oculi
photography range from about 350 nm to 750 nm, which wavelengths
fall in the visible wavelength range. Also, in fluorescent
photography, an absorption center wavelength is about 490 nm, while
a fluorescence center wavelength is about 577 nm. In infrared
fluorescent photography, an absorption center wavelength is about
766-795 nm, while a fluorescence center wavelength is about 826-835
nm.
Hence, in the present embodiment, a filter having a transmission
characteristic as shown in FIG. 7(a) so as to transmit only
exciting light corresponding to the above wavelength condition for
fluorescent photography is used as the exciter filter 30a for
fluorescent photography, and a filter having a transmission
characteristic as shown in FIG. 7(b) so as to transmit only
exciting light corresponding to the above wavelength condition for
infrared fluorescent photography is used as the exciter filter 30b
for infrared fluorescent photography. Also, a filter having a
transmission characteristic shown in FIG. 8(a) is used as the
barrier filter 31a for fluorescent photography, and a filter having
a transmission characteristic shown in FIG. 8(b) is used as the
barrier filter 31b for infrared fluorescent photography.
As seen from FIG. 8, the transmission characteristic of the barrier
filters 31a and 31b is extended only to the longer wavelength side.
Thus, the barrier filter 31a does not transmit exciting light
(about 450-525 nm) which has passed through the exciter filter 30a
having a transmission characteristic shown in FIG. 7(a), but can
transmit fluorescent (about 520-650 nm) in fluorescent photography
and light having longer wavelengths than the fluorescent light.
Also, the barrier filter 31b does not transmit exciting light
(about 700-800 nm) which has passed through the exciter filter 30b
having a transmission characteristic shown in FIG. 7(b), but can
transmit infrared fluorescent light (about 820-940 nm) in infrared
fluorescent photography and light having longer wavelengths than
the infrared fluorescent light.
These characteristics reveal that in order to detect focusing in
any of ordinary photography, fluorescent photography, and infrared
fluorescent photography, at least, a center wavelength of the light
source 16 for projecting an indicator or collimating mark should be
substantially longer than a center wavelength of infrared
fluorescent light. At this time, light from the light source 16
needs to pass through both the barrier filter for fluorescent
photography and the barrier filter for infrared fluorescent
photography. Furthermore, the dichroic mirror 14 has the
characteristic of reflecting light of the light source 16, which
light has substantially longer wavelengths than a center wavelength
of infrared fluorescent light, and of transmitting light having
shorter wavelengths than a center wavelength of infrared
fluorescent light. The dichroic prism 7 has, also, a characteristic
of reflecting light from the light source 16 and transmitting light
having wavelength shorter than that of light form the light source
16. A dichroic mirror may be used in place of the dichroic
prism.
Photographic methods using the above-mentioned ophthalmic
photographic device according to the present embodiment will now be
described briefly.
Ordinary Photography
In this case, neither of the exciter filters is placed between the
ring slit 5 and the relay lens 6, and neither of the barrier
filters is placed between the relay lens 13 for focusing and the
dichroic mirror 14. Accordingly, the fundus oculi of the eye 12 to
be examined is illuminated by light from the light source 1 for
observational illumination in the illuminating optical system 101
and by infrared light from the light source 16 for projecting an
indicator in the indicator projecting optical system 102. An image
of the fundus oculi is focused by the focusing detection optical
system 103 in the manner described before by means of infrared
light reflected by the dichroic mirror 14. The observational
optical system 104 allows an examiner to observe the image of the
fundus oculi. The image of the fundus oculi is photographed on the
photographic image plane 15 by light emitted from the stroboscopic
tube 4.
Fluorescent Photography
In this case, the exciter filter 30a is placed in the optical path
between the ring slit 5 and the relay lens 6, and the barrier
filter 31a is placed in the optical path between the relay lens 13
for focusing and the dichroic mirror 14. Accordingly, the fundus
oculi to be examined is illuminated by exciting light, i.e., light
which has passed through the exciter filter 30a after having been
emitted from the light source 1 for observational illumination in
the illuminating optical system 101, and by infrared light from the
light source 16 for projecting an indicator in the indicator
projecting optical system 102. The exciting light causes the fundus
oculi to emit fluorescent light. Fluorescent light and infrared
light reflected by the fundus oculi pass through the objective lens
11 and the relay lens 13 for focusing and then advance through the
focusing detection optical system 103 and the observational optical
system 104. An image of the fundus oculi is focused by the focusing
detection optical system 103 in the manner described before by
means of infrared light reflected by the dichroic mirror 14. The
observational optical system 104 allows an examiner to observe the
image of the fundus oculi having passed through the dichroic mirror
14. When the image of the fundus oculi is to be photographed, the
quick return mirror 27 is lifted up, and the image is photographed
on the photographic image plane 15 by fluorescent light which is
emitted from the fundus oculi as a result of stimulation by
excitation light, i.e. light which has passed through the exciter
filter 30a after having been emitted from the stroboscopic tube
4.
Infrared Fluorescent Photography
In this case, the exciter filter 30b is placed in the optical path
between the ring slit 5 and the relay lens 6, and the barrier
filter 31b is placed in the optical path between the relay lens 13
for focusing and the dichroic mirror 14. Accordingly, the fundus
oculi to be examined is illuminated by exciting light, i.e., light
which has passed through the exciter filter 30b after having been
emitted from the light source 1 for observational illumination in
the illuminating optical system 101, and by infrared light from the
light source 16 for projecting an indicator in the indicator
projecting optical system 102. Exciting light causes the fundus
oculi to emit infrared fluorescent light. Infrared fluorescent
light and infrared light reflected by the fundus oculi pass through
the objective lens 11 and the relay lens 13 for focusing and then
advance through the focusing detection optical system 103 and the
observational optical system 104. An image of the fundus oculi is
focused by the focusing detection optical system 103 in the manner
described before by means of infrared light reflected by the
dichroic mirror 14. The observational optical system 104 allows an
examiner to observe the image of the fundus oculi by means of light
having passed through the dichroic mirror 14 (in this case TV
monitor is preferable). When the image of the fundus oculi is to be
photographed, the quick return mirror 27 is lifted up, and the
image is photographed on the photographic image plane 15 by
infrared fluorescent light which is emitted from the fundus oculi
as a result of stimulation by exciting light, i.e., light which has
passed through the exciter filter 30b after having been emitted
from the stroboscopic tube 4.
As has been described above, the ophthalmic photographic device of
the present invention enables focus to be detected in fluorescent
photography and infrared fluorescent photography as well as
ordinary photography.
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